Callianassa subterranea (Montagu, 1808)

Dworschak, Peter C. & Poore, Gary C. B., 2018, More cautionary tales: family, generic and species synonymies of recently published taxa of ghost and mud shrimps (Decapoda: Axiidea and Gebiidea), Zootaxa 4394 (1), pp. 61-76 : 64-66

Callianassa subterranea (Montagu, 1808)

( Figs 2 , 3 )

Cancer Astacus subterraneus Montagu, 1808: 88, pl. 3 figs 1, 2.

Callianassa subterranea .— Ngoc-Ho 2003: 468 –472, figs 9, 10.— Sakai 2011: 360 (complete synonymy).— Sakai & Türkay 2012: 734 –735, fig. 5.

Trypaea vilavelebita Sakai & Türkay, 2012: 741 –746, figs 8, 9. Syn. nov.

Material examined. North Sea , Oyster Ground? (REINECK box cores), NHMW 6783 (ovigerous female, 11.0 mm; 4 females, 3.9–9.0 mm; 2 males, 2.8, 10.0 mm; fragments of 6 specimens). Aegean Sea, 92 m (Pola Expedition stn 227) , NHMW 6613 (female, 3.8 mm). Tyrrhenian Sea, Livorno, Secce della Meloria , Posidonia rhizomes , NHMW 25023 (male, 10.3 mm). Adriatic Sea, Rovinj, off Polari, NHMW 19597 (male, 4.6 mm; female, 4.0 mm; ovigerous female, 4.3 mm). Rovinj, Pirozi, 25–32 m, NHMW 18376 (2 males, 3.6, 2.8 mm); NHMW 19941 (2 males, 3.4, 2.6 mm; female, 3.4 mm); NHMW 19949 (2 males, 4.6, 2.5 mm; female, 4.1 mm; ovigerous female (pleon only); juvenile, 1.8 mm); NHMW 20482 (male, 3.6 mm; female, 3.7 mm); NHMW 25024 (4 males, 2.6–4.9 mm; 2 females, 3.6, 2.9 mm); NHMW 25 235 (2 males, 3.7, 2.1 mm; female, 4.0 mm; juvenile, 1.9 mm); NHMW 25641 (5 males, 3.6–4.5 mm; ovigerous female, 4.8 mm); NHMW 25758 (male, 5.0 mm); NHMW 25759 (ovigerous female, 5.2 mm); NHMW 25760 (male, 3.6 mm).

Remarks. Sakai & Türkay (2012: 745) stated that their new species differed from C. subterranea as follows: “In T. vilavelebita sp. nov. the A1 peduncle is slightly longer than the A2 peduncle (vs. the A1 peduncle is slightly shorter than the A2 peduncle, see Ngoc-Ho, 2003, fig. G, H [sic]; Sakai, 2005, fig. 7G, H), the male Plp1 is uniramous and bisegmented (vs. the male Plp1 is uniramous and uni-, bi-, or trisegmented, see fig. 5A), and the male Plp2 is absent (vs. male Plp2 is uniramous (fig. 5B), though rarely biramous by deformed protopod protruded short distolaterally).” This is not supported by their figure of the holotype ( Sakai & Türkay 2012: fig. 8A), which shows the peduncle of the antenna to be clearly longer than that of the antennule. Only in dorsal view (fig. 9A) does the antennule appear shorter than the antennal peduncle, probably because it is was not illustrated in the horizontal plane.

The observed differences from C. subterranea in presence/absence of pleopod 2 of the male, which prompted them to place the species in another genus, represent two stages of maturity. The development of both pleopods 1 and 2 is a secondary sexual character. Small males often lack or show only a vestigial pleopod 2, whereas it is well developed in larger specimens. Ngoc-Ho (2003) has reported that in C. subterranea the male pleopod 2 is sometimes absent. Male pleopods 2 are also often absent in C. ceramica (see Poore & Griffin 1979: 260) and Dworschak (2003) demonstrated the variability of pleopods 1 and 2 over the entire size range in C. aqabaensis .

We refrained from requesting the type material of T. vilavelebita on loan as “All of the present specimens examined were extensively damaged and no complete specimens were collected” ( Sakai & Türkay 2012: 745).

Most of our study material comes from one population in the Adriatic Sea near Rovinj, not far from the localities of C. subterranea reported by Sakai & Türkay (2012) and the type locality of T. vilavelebita . In fact, they reported both species from the same sample (stn SJ-005 [erroneously as JS-005 on p. 735], 45°18.4'N, 13°08.0'E, 31 m). Our examples have been collected mainly with a Van Veen grab from a muddy bottom between 25 and 32 m water depth and consist of small specimens with CL ranging from 1.8 to 5.0 mm. Some specimens with CL 1.8–5.0 mm showed no trace of pleopod 2 ( Fig. 2A ) while others of CL 2.1–4.9 mm had a vestigial bud-like pleopod 2 ranging in length from 35 to 392 µm ( Fig. 2B ). Only the largest male available (from Livorno) had a biramous pleopod 2 1400 µm long ( Fig. 2C ). The relationship between the lengths of male pleopods 1 and 2 and carapace length is shown in Fig. 3 .

It is concluded that Trypaea vilavelebita is not a valid species but represents juvenile Callianassa subterranea with an undeveloped pleopod 2. The former is thus synonymised with the latter.

Figures

FIGURE 2. Callianassa subterranea (Montagu, 1808). A, NHMW 25024 (male, 2.4 mm), pleomeres 2 and 3, ventral aspect; B, NHMW 25641 (male, 4.3 mm), pleomeres 1–3, lateral aspect; C, NHMW 25023 (male, 10.3 mm), Plp2, ventral aspect. Scale bar = 1 mm.

FIGURE 3. Callianassa subterranea (Montagu, 1808). Relationship betWeen the lengths of male pleopods 1 and 2 and carapace length.